Gauge for linear lamps



2 Sheets-Sheet l Ot- 19, 1954 D. L. PEARSON GAUGE FOR LINEAR LAMPS FiledJuly 15, 195s n, O `MOSWMW P s /M e vmfA mm .s o H s m.\ O Qm' O D i*A AID Oct- 19, 1954 D. PEARSON 2,691,825

GAUGE FOR LINEAR LAMPS Filed July 13, 1953 2 Sheets-Sheet 2 Figl. y@

Invenclor: Dorwelbcnl` L. Pearsom, 135W@ His Aftfto meg.

Patented Oct. 19, 1954 GAUGE FOR LINEAR LAMPS Donald L. Pearson, Euclid,Ohio, assignor to General Electric Company, a corporation of New York vApplication July 13, 1953, Serial No. 367,435

l 2 Claims. 1

The present invention relates to gauges and more particularly to gaugesfor measuring the linear distance between spaced parts of doubleendedelongated electric lamps, such as electric discharge fluorescent lampshaving tubular linear glass envelopes coated internally with fluorescentpowder and having helically coiled fllamentary electrodes sealed in theends of the envelopes with their longitudinal axes transverse to thelongitudinal axes of the envelopes.

Lamps of this type are made in standard lengths to engage lamp holdersspaced apart to accommodate the lamps therebetween. Consequently, in theproduction of such lamps, the manufacturing tolerances must be coniinedwithin limits such that the usual contact pins protruding from the basesprovided at the ends of the lamp envelope engage the lamp supporting andelectrically conductive parts of the lamp holders. In the manufacture ofsuch lamps the spacing between the shoulders provided at the ends of theglass envelope and against which the bases abut must be accuratelycontrolled within close tolerances, because this spacing determines theover-all length of the based lamp. l

Further, the electrical characteristics of such lamps are influenced bythe length of the gap between the electrodes and it is necessary alsointhe manufacture of such lamps to Acontrol the electrode spacingaccurately. Direct visual inspection of the electrodes in the lampenvelope to measure the gap between them is not possible, because theenvelope is made translucent by the coating of fluorescent powder.

The principal object of the present invention is to provide aninspection gauge in which means is provided for accurately measuring thespacing I between the electrodes of such lamps. A further object of theinvention is .to provide such a gauge which is capable of measuring theelectrode spacing without in any way marking or disturbing the structureof the lamp, to the end that numerous lamps may be measured forinspection purposes and the sample lamps then sold commercially if theelectrode spacing is within accepted toler ances. Still further objectsand advantages of the invention will appear from the following detaileddescription of a gauge embodying the invention.

The above objects of the invention are attained by a gauge including asone of its features light electrodes to be cast on a Wall of theenvelope. Another feature of the gauge is the provision of means toeliminate parallax and a direct reading means to indicate the length ofthe electrode gap as indicated by the spacing of the shadows.

In the accompanying drawings,

Fig. l is a side elevational view of a gauge embodying the invention;

Fig. 2 is a similar view of a fluorescent lamp of the type to bemeasured by the gauge;

Fig. 3 is a top plan view of the gauge shown'in Fig. 1;

Fig. 4 is an end section taken along the line 4-4 of Fig. 3, and

Fig. 5 is a schematic illustration of an optical system useful in thegauge shown in Figs. 1 to 3.

Referring to Figs. 1 and 4 of the drawing, the gauge comprises a pair ofspaced cups 1 and 2 supported in opposing positions by blocks 3 and 4bolted to the ilat support plate 5. The Cups are shaped to provide anannular seat for the annular shoulders 6 and 'I at the ends of thetubular lamp envelope 8 (Fig. 2). The gauge is provided with a pair ofspaced aligning rods 9 and III extending through and engaging the blocks3 and 4 and also the intermediate block I I bolted to the plate 5 toalign the cups I and 2 with these seats in parallelism.

The cup I is mounted in fixed position on block 3, whereas cup 2 ismounted on one end of the straight shaft I2 extending through the block4 and movable longitudinally therein. Thus, the cup 2 is movable in thedirection of the fixed cup I. A coiled metal spring I3 is mounted aroundthe shaft I2 and between the block 4 and the cup 2, to bias the cup 2toward the opposite cup I. The spacing of these parts is such that thelamp envelope 8 may be mounted on the gauge by moving cup 2 in thedirection away from cup I, placing the envelope 8 (indicated in brokenlines in Figs. 1, 3 and 4) between the cups and then releasing cup 2which is biased by the compressed spring I3 toward its originalposition. The envelope t is thus firmly clamped between the cups I and2.

The opposite end of the shaft I2 is rigidly connected by the link Ill tothe end of the piston I5 of an air cylinder I6 mounted on the block 4.The return motion of the shaft I2 under the action of the spring I3 onrelease of the cup 2 is dampened by the piston I5 and the cylinder I5 toavoid shattering the envelope 3 and also to protect the dial gauge 2 I,described below, from physical shock.

A rigid cross arm Il is fixed tc the shaft I2 and to another shaft I3which extends through the sleeve I9 fastened to the block ll and also asleeve 20 fastened to the intermediate block l I. A conventionalindicating dial gauge 2l is also attached to the intermediate block Hlby the bracket 22 with the spring pressed arm 23 thereof aligned withand engaging the end of the shaft i8. Any movement of the cup 2 istransmitted by the above-described mechanism to the indi-` cating dialgauge 2l. Variations in shouldentoshoulder length of the lamp envelopesmeasured by the gauge are thus easily detected by the above-describedparts of the mechanism and are indicated by the dial gauge 2|.

The mechanism may be used for making shoulder-toshoulder measurements oflamp envelopes either before or after the electrodes 24 and 25 (Fig. 2)have been sealed into the ends of the lamp envelopes.

rIhe other parts of the gauge shown in the drawing and described beloware useful for measuring the gap between the lamp electrodes 2t and 25after these have been sea-led into the envelope 8 and the manufacture ofthe lamp has been completed except for the mounting of the usual bases(not shown) on the ends of the lamp envelope 8 and butting against theshoulders G and l thereof.

The parts of the gauge useful for measuring the length of the gapbetween the electrodes 2f and 25 comprise two light projectors 2S and 2lof similar structure constructed and Iarranged to project parallel beamsof diverging light rays through the lamp envelope 3 in the region of theelectrodes 24 and 25 and in a direction trans verse to the longitudinalaxis of the envelope 8 mounted in the cups l and 2. ln using the gaugefor the purpose contemplated the lamp envelope 8 is mounted in the cupsl and 2 with the straight longitudinal axis of each of the coiiedfilamentary electrodes 24 and 25 transverse to the axis of the beams ofdivergent rays projected by the projectors, as shown diagrammatically inFig. 5. A shadow of each of the electrodes thus is cast on a part of thewall of the envelope t away from the light projector. The envelope S ismade translucent by 'the usual coating 22 of fluorescent powder on itsinner surface (Fig. 2). For convenience, the portion of the envelopewall on which the shadow of the electrodes is cast is Flcrsignatedhereinafter as the shadow wall.

The light projectors 26 and 2l? each comprise a housing 3G, light tightexcept for a pin hole aperture Si in its wall 32 (Figs. 1 and 5) facingthe envelope 2, a light source mounted in the housing Sil and in theform of an incandescent lamp 33 (Fig. 5) having a concentrated lament,and an optical system also mounted in the housing and made up of thecondensing lenses 3d and 35 which focus light from the filament of thelamp 33 in the aperture 3l in the wall 32.

The housings 3B are each mounted on a slider` 35 engaging a slideeway3l. The slide-ways 37 are fastened to plate and extend parallel to thepath between the cups I and 2. The light projectors 26 and 2l thus areadjustable on the plate 5 to bring their pin hole apertures 3l oppositethe electrodes 24 and 25 of individual lamps supported by cups I and 2and to be inspected for electrode spacing.

In order to prevent parallax, a. narrow opaque pointer 33 of the samewidth as the shadow cast is attached to each of the sliders 36 by thearm 39 (Fig. 4) and is positioned directly in line with the pin holeaperture 3| in wall 32 and opposite the shadow wall of the lamp envelope3. When each of the projectors 26 and 21 are in such position relativeto a lamp to be inspected for electrode spacing that each of the shadowscast by the electrodes on the shadow wall are directly opposite therespective pointers 38, then the aperture 3l, the respective electrode24 or 25, the shadow 4and the pointer 38 are all in the same straightline and parallax is eliminated.

The distance between the lamp electrodes, which may vary slightly fromlamp to lamp, may then be accurately measured by suitable means havingindicating elements, the relative position of which to each other isdetermined by the spacing of the projectors 25 and 2.

This measurement is conveniently made in the embodiment of the inventionshown in the drawings by the indicating gauge comprising the slide baril movable in the slide-ways il fastened to the plate 5. The slide barlil is secured by arm 42 at one of its ends to the arm 39 of the lightprojector 26, so that it moves with the light projector 26. The pointeri3 of the indicating gauge is similarly fastened on the arm 39 of thelight projector 2l (Fig. 4) and terminates in juxtaposition to the scalete (Fig. 3) on the slide bar 4Q. The slide bar Il@ and the pointer G3are so secured to the respective light projectors 25 and 2l and thescale Llc on the bar lll is so calibrated that the length of the gapbetween the electrodes 2li land 25 is readable directly on the scale edwhen the electrode shadows are directly opposite the pointers 38 on theprojectors. Electrode gaps of approximately thirty-eight inches and morein length can be quickly measured with an accuracy of plus or minusone-half millimeter by the gauge of this invention to facilitateinspection of liuorescent lamps without disturbing the lamp. structure.

While I have shown and described a particular embodiment of myinvention, it will be understood of course that changes in the form anddetails of the gauge shown may be made by those skilled in the artwithout departing from the spirit and scope of the invention; forexample, a dial gauge similar to gauge 2l suitably connected to theprojectors 26 and 2l may be used in place of the sliding scale andpointer assembly for measuring the spacing between the electrodes.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A gauge for measuring the spacing of the electrodes at the ends ofdouble-ended tubular linear lamps having translucent envelopes,comprising light projector means directing parallel beams of light inthe same direction from a common plane and including means forindividual adjustment of the beam projecting elements thereof whereby toeiect changes in the relative spacing of said parallel beams, an opaquepointer aixed to and spaced from each of said beam projecting elementsfor movement therewith and positioned in the axis of the respectiveprojected beams, means for supporting a lamp envelope between saidcommon plane and said pointers with the ends of said envelope in thepath of said projected beams whereby to cause a shadow of each of thelamp electrodes to be cast on the light diffusing wall of said envelopein the vicinity of the respective pointers, and means also aflixed toeach of the said beam projecting elements for movement therewith andcalibrated to indicate the spacing between said electrodes when theirshadows are directly beneath said pointers.

2. A gauge for measuring the spacing of the electrodes at the ends ofdouble-ended tubular linear lamps having translucent envelopes,comvelope between said common plane and said pointers with the ends ofsaid envelope in the path of said projected beams whereby to cause ashadow of each of the lamp electrodes to be cast on the light-diffusingWall of saidy envelope in the vicinity of the respective pointers, andmeans also aiiixed to each of said projectors for movement therewith andcalibrated to indicate the spacing between said electrodes when theirshadows are directly beneath said pointers.

No references cited.

